1. Field of the Invention
The present invention is in the field of hypodermic syringes used to inject and aspirate liquid material from a patient. More particularly, this invention is directed to render a syringe non-reusable syringe with an engageable retractable cap for the entire needle.
2. Description of the Prior Art
Hypodermic syringes with attached needles are used for the administration of medication and for the withdrawal of material from a patient. These syringes are generally disposable which presents two problems, one is the possible reuse of a syringe and the other and greatest danger is the possibility of being pricked by the needle when handling the syringe. These two concerns are particularly important because the needle and or the syringe may be contaminated and spread disease, such as hepatitis and acquired immune deficiency syndrome (AIDS).
The known non-reusable syringes can easily be reused. In addition often times needles need to be visible for injection. Some devices provide for a shield where the needle is recessed to prevent possible pricking; however, these devices do not provide for a seal directly over the needle whenever the needle is not in use and the neddle is not visible for proper injection. The apparatus of U.S. Pat. No. 4,795,432 to Karczmer does provide a cap at the end of its shield assembly; however, this not only prevents pricking but it also prevent multiple exposure of the needle tip which is sometimes necessary, especially when withdrawing blood for testing. The inventions of U.S. Pat. Nos. 4,507,118 to Dent and 4,767,413 to Haber provide caps but the syringe needle is designed to pass through these caps. Once the needle passes through the caps in these patents, the caps are no longer act as a complete seal to prevent any leakage.